Well sampler



United States Patent Office Patented Nov. 19, 1968 3,411,587 WELL SAMPLER Claude Lucien Bournazel, Cemay-la-Ville, France, as-

signor to Societe de Prospection Electrique Schlumberger, S.A., Paris, France, a corporation of France Filed Jan. 4, 1967, Ser. No. 607,280 6 Claims. (Cl. 166-165) ABSTRACT OF THE DISCLOSURE A well liuid sampling device includes a central conduit which is small in cross section compared to the well bore. A packer isolates fluid flow to the conduit. One end of a sample tube projects axially into the conduit and communicates at its other end with the sample chamber. A valve operable from the surface permits fluids owing through the conduit to divert through the sample tube into the sample chamber. Another valve operates automatically in response to filling of the sample chamber to close off lluid ow into the sample chamber.

The present invention relates to an apparatus for sarnpling uids in a borehole, and, more particularly, for sampling production uids from oil-producing petroleum wells.

A method resorted to up to now for sampling the fluids in a borehole consists in lowering a fluid sampling chamber into a borehole and opening the chamber at a predetermined level to permit fluids present at the level to enter the chamber. The chamber is then closed and recovered for subsequent analysis of the sample. With such a method, the samples removed from the borehole are not actually representative of the uids produced in the well. For example, it is a well-known fact that water from the producing formations accumulates at the lower portions of a well ydue to the density of the water. While a small fraction of such water can be carried out of the well by the oil or gases produced, in most cases, the oil-containing or gas-containing formations are covered by a mass of water which is more or less static. Consequently, the oil or gases owing from the formations must move through a column of such accumulated water. Hence, it is obvious that, at a given level, the composition of the mixture of fluids appearing there can be very different from the composition ofthe iluids produced from the formations. The same is true for a well producing oil and gas. The actual rising speed or velocity of gas bubbles through the oil is such that the fluids ow at very different speeds. For this reason, the relative amounts of fluids appearing at any moment between two levels in a well do not represent the actual fluid production of the well. It is, therefore, easy to understand wly, under such conditions, it has been impossible hitherto to obtain representative samples of the uids owing in a producing oil Well.

It has been attempted to eliminate the foregoing ditliculty by stopping the oW of the well during the sampling operation. In such case, the fluids separate through differences in specific gravity and, after a certain time, an equilibrium is obtained. The level of separation between the heavy and light fluids is then detected, generally by a measure of specific densities, and removal of a fluid sample is executed at the desired level. Such an operation is obviously lengthy and in numerous cases it is of little benefit. This is the case in particular when several iiuidcarrying formations feed the same well. Such formations are generally at different pressures so that fluid migration occurs between the formations as soon as the well is closed. Furthermore, since oils of dilerent specific gravities are miscible, it is impossible to obtain a separation in accordance with the specific gravities of different oils produced by several formations. Furthermore, when it is desired to ascertain the amount of water moving at a predetermined level, it is obvious that the method now used will not provide accurate results. It should also be mentioned that in the case where closing olf the well may lead to formation damage, sampling in situ is not generally preferred. This is particularly the case for wells which are steam injected. t

An object of the present invention is to provide a new and improved apparatus for obtaining representative samples of fluids producing from a petroleum well without stopping the production ow of the well.

According to the invention, a sampling device is suspended from a cable, the sampling device including a passageway with a small cross section and an inflatable packer for isolating producing fluid flow to the passageway. One end of a sampling tube is axially projected into the passageway, while the other end of the flow tube communicates with a sample chamber. A valve is operated from the surface to permit producing fluids to flow through the sampling tube into the sample chamber. A controlled back pressure is provided against the iiow of fluids into the sample chamber. A valve automatically closes the sample chamber upon filling thereof.

The recovered sample contains the fluids produced by the fluid-containing formations located underneath the packer. In fact, the system consisting of the packer and the passageway causes a separation between the static fluids and the dynamic fluids moving inside the well. By reason of the reduced cross section of the central passageway, only the moving dynamic fluids are passed through the passageway after setting the packer. By placing the fluid sample chamber in communication with the passageway, the sample under such conditions is that of uids moving at the level at which the apparatus is positioned.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of embodiments when taken in conjunction with the accompanying drawings in which:

FIGURE l illustrates a sampling device as it appears during the lowering thereof inside a well; and

FIGURE 2 illustrates the sampling device at the moment the sample-receiving operation is at an end.

In FIGURE l, 10 designates a petroleum producing well bore. A fluid sampling device 14 is connected through connection 16 with a packer 18 and the assembly is lowered into the well or borehole 10l by means .of a cable 12 having electrical conductors.

The fluid sampler 14 is comprised of a housing 20 having an auxiliary chamber 22 containing air under atmospheric pressure and a fluid sampling chamber 24. A throttled passage or orifice 26 provided with an electrically controlled valve member 28 connects the chambers 22 and 24 With each other. Such an electrically controlled valve for similarly connecting chambers in a well sampler is shown in U.`S. Patent No. 3,095,930. The chamber 24 which is smaller than the chamber 22, is filled with silicone oil subjected to pressure, Any other liquid which is not miscible with the water, gases and oil found in a petroleum well, may be used as well. A free piston 30 is disposed near the bottom of chamber 24. A valve seat 31 is formed in the inlet 32 of the chamber 24. A flexible line or wire 21 is connected between the free piston and a valve closure plug 25 complementally shaped for seating with the valve seat 31. Seal means 30a, on the lower side of the piston, normally engage the valve sanas? seat 31 to close the passage 32 when the piston 30 is in the position shown in FIGURE 1. As soon as the piston moves upwardly, the valve seat 31 is uncovered and upon further upward movement of piston 30 into engagement with the abutment formed by the upper end of chamber 24, the line 21 becomes taut and thus the plug 25 is received in the valve seat 31. The inlet 32 of the chamber 24 is connected to a sampling tube 33 which extends downwardly into a central passageway 42.

The packer 18 includes a hydraulic section 34, having a conventional type hydraulic system which includes a lift and force pump P controlled, as by an electrical conductor in the cable 12, from the surface. The hydraulic system serves to inject well iluids under pressure via a conduit 27 into an inilatable packer element 36. Well fluids enter the hydraulic section by way of ports 45 and are filtered by filter element 47. The well fluids are transmitted from the pump P to the packer element by means of passageway 27. The packer element 36 has a substantially cylindrical shape and is secured at its lower end, 4in a iluid tight relationship, to a supporting member 35 and at its upper end to a sliding ring 37. A tension spring 38 is compressed between the supporting member 35 and the ring 37. The ring 37 is adapted to slide over the periphery of a cylinder 4@ forming the wall of the central passageway 42. When it is desired to inllate the packer, the force pump P in the hydraulic section is actuated to pump well lluids through passageway 27 into the annular space between the packer element 36 and cylinder 40. Introduction of tluid under pressure into the annular space causes the packer element 36- to expand outwardly, Such outward expansion is permitted by downward movement of ring 37 against the force of spring 3S until the well bore is sealed oil.

The passageway 42 has a cross section equal to a few square centimeters. The passageway 42 is provided with inlets at 44 and with outlets at 46 which are respectively below and above the packer element 36. The fluid sarnpling tube 33 opens into the passageway 42 below the outlet 46. For convenience of illustration, drops of oil are illustrated by the number 50 and would pass upwardly through water 48 in the well.

When the apparatus is lowered into the well 10, the packer element 36 is deflated in the manner shown in FIGURE 1. Under such conditions, the central passageway 42 carries a mixture of water and oil which is substantially identical with the surrounding mixture of water and oil in the well bore. FIGURE 1 shows that, if the mixture contained at such a moment in the central passageway 42 were trapped as a sample, the fluids thus recovered would not form a representative sample of the lluids moving inside the well. It is emphasized that the sampler must recover a representative sample of the producing or moving fluids in the well bore. A sample of lluids shown in FIGURE l would in fact contain an amount of water which is much larger than that which is actually produced from the earth formations.

As shown in FIGURE 2, when the packer element 36 has been inflated by the hydraulic section 34 so as to pack ofi the well, the standing water is separated from the production iluids such as oil and water moving inside the well. As a matter of fact, after inllating the packer 36, almost the entire amount of water contained initially inside the central passageway 42 is quickly driven out by the'production oil which, in spite of the presence of the packer, continues moving upwardly. In order for this to occur, it is necessary, of course, for the ratio between the cross section of the passageway 42 (equal to a few square centimeters) and the cross section of the well 1l) (equal to a few square decimeters) to be lower than the ratio between the relative volumes of oil and water appearing in the well between the levels defined by the inlets 44 and the outlets 46 of the central passageway 42.

The time required for separation of the standing water from production lluids is comparatively short and, to this end, shortly after the positioning and inating of the packer, the valve member 28 is electrically operated so as to open the orifice 26 to permit fluid to flow from chamber 24 into chamber 22. The silicone oil which at first is under pressure inside the fluid sampling chamber 24 begins to rise -immediately into the auxiliary chamber 22. The throttled port or orifice 26, which may of course be adjusted, defines the speed of the fluid rising into chamber 22 and thus controls the back pressure imposed on the producing lluids. While the silicone toil rises into the chamber 22, the piston 30 rises inside the chamber 24 and opens the valve seat 31. The fluid sampling tube 33 in the central passageway 42 draws the oil into the chamber 24 ybehind the rising piston. As soon as the piston 30 reaches the upper end of the chamber 24, the wire 21 becomes taut to pull the closure plug 25 into the valve seat 31 to thereby close the passage 32 while the piston 30 closes the orifice 26. Latches or detents (not shown) may be provided in the sample taking mechanism to lock the valve plug 25 and piston 30 in their closed and upper positions, respectively, after the sample has been taken. This will prevent any changes in differential pressure during the operation from reopening the valve seat 31 or moving piston 30 downwardly.

The chamber 24 now carries a sample of the fluids (oil and water) produced by the oil-containing layers located underneath the level at which the packer has #been positioned. If any traces of sil-icone oil are still present in the sample, it is easy to ascertain this during the analysis. After a sample has been taken, the hydraulic section 34 is operated to deflate the packer element 36 which under the action of the spring 38 returns into its inoperative posit-ion as illustrated in FIGURE 1. The apparatus is then raised.

As an alternative arrangement, the fluid sampling ap` paratus 14 may be of the type illustrated in U.S. Patent No. 3,095,930 which is assigned to Schlumberger Technology Corporation. A sample chamber similar to that disclosed herein is also set forth in greater detail in U.S. patent application Ser. No, 582,956 which is also assigned to Schlumberger Technology Corporation.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its 'broader -aspects and, therefore, the aim in the appended -claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. An apparatus for obtaining a representative sample of producing fluids in a well bore comprising: a housing adapted to be suspended from a cable for passage through a well lbore to a level where a fluid sample is desired, packer means secured to said housing, means on said housing lfor expanding and contracting said packer relative to said housing, a central passageway formed longitudinally through said housing, inlet and outlet ports communicating said passageway with the exterior of said housing respectively `below and above said packer means, a sample chamber in said housing, a sample tube eX- tending axially into said passageway and communicating with said sample chamber for diverting fluids from said passageway into said sample chamber, and selectively operable valve means permitting producing lluids to flow into said sample chamber.

2. The apparatus of claim 1 wherein `said sample tube extends into said passageway to a point below said outlet port.

3. The apparatus of claim 1 wherein the ratio between the cross-sectional area of the passageway and the crosssectional area of the well bore is lower than the ratio between the relative volumes of' oil and water in the well bore at the level at which the sample is to 'be taken.

4. The apparatus of claim 1 wherein said packer means includes a fluid inflatable packer element and said packer expanding means includes a hydraulic system for providing fluid under pressure to said packer element.

5. The apparatus of claim 1 wherein said sample chamber includes means for producing a back pressure against producing fluids owing into said sample chamber.

6. The apparatus of claim 5 wherein said back pressure producing means includes an auxiliary chamber, piston means for transferring fluid lfrom said sample chamber to said auxiliary chamber and Iorifice means for impeding the ow of Huid from said sample chamber to said auxiliary chamber.

References Cited UNITED STATES PATENTS Lindsly 166-165 Parks 166-165 X Lindsly 166-165 X Desbrandes 166-162 Barry et al. 166--3 Voetter 166-163 10 DAVID H. BROWN, Primm Examiner. 

